@theo_dufort , thank you for the extra information/context.
Anecdotally, as an Instructor, the change from unmuting an assignment to posting an assignment hadn't changed my release pattern at all. I'm doing things the exact same, I just had to set things up a bit differently now at the beginning of the semester. Yet, I can see where it might be interesting to review data related to this to see if I'm the exception or the norm.
I happened to have lunch with someone who does program and knows the API (aka, the hubby) and he indicated that there wouldn't be anything attached to the assignment to indicate if it was created when the faculty member was using the new or old gradebook. As a side note, a faculty member could have created the assignment using the old gradebook, but then switched to using the new gradebook at a later date. I actually had this happen this month. All the assignments for a course were created while I was using the old gradebook, we then switched to the new gradebook before any assignments were due, and now all of my "posting" (unmuting) of grades so far this semester was done using the new gradebook (even though the assignments were created using the old gradebook).
I wonder if it would work better if you looked at the question in a different way. So not when were the assignments created, but how many assignments were "hidden." (so made use of the grade posting policy) when using the new gradebook VS how many assignments were "muted" when using the old gradebook. Granted, I don't know what is available in the API, so maybe you'd need to look at how the grades were released. I did a quick search and this was the only post I could find related to the new Grade post policy and the API - How to read and change Course Post Policy of the New Gradebook with GraphQL. Still crossing my fingers that someone with actual API knowledge will jump in here and help out.
Kona
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